Spelling out clearer signs

Clearer roadside displays that really grab drivers’ attention, while using very little electric power, are promised in WO 0196666. They have a matrix of reflective glass beads topped by an array of opaque plastic coils. Normally the coils are wound up, exposing the beads below them. But applying a voltage to a particular coil makes it unwind and block the view of the bead. Display Science of Massachusetts suggests pulsing the voltages to create a pattern of illuminated dots which can spell out brightly flashing messages.